The Basic Winter Technique - All of the hex styles you have read about in standard terrain are used in a winter board. They just have to be covered with snow rather than grass. And the trees are bare, or snow-covered conifers. The deciduous trees are now modeled from braided picture hanging wire, which is sold in hardware stores. Get several different thicknesses, especially the heavier gauges. These are used to make bare trees, which, though fragile, add a great deal of realism to any winter scene.
Modeling Ice - We could cover ice with snow, but that really gets boring. A much more pleasing effect is to model translucent, grey ice, occasionally blanketed by drifted snow. Again using all water-based materials, this is an easy project. Ponds and rivers can be created using the same techniques.
To add a great detail to the banks, use picture wire to model brush without summer foliage. Simply fray a piece of the wire, and "plant" it beside the frozen streambed.